Experimental analysis of 5G pilot signals' variability in urban scenarios

This paper deals with radio-frequency electromag-netic field (RF -EMF) exposure from stand-alone (SA) 5G massive-MIMO radio base stations (RBSs) operating in the sub-6 GHz frequency range (FRl). In general, the basic principle for human exposure is to measure the power received from a constant radio control signal (usually called a pilot signal) and to apply a proper extrapolation factor, already defined in cases of 2G, 3G, and 4G RBSs. As for 5G NR (New Radio), the use of beamforming, flexible numerologies, and Time Division Duplexing (TD D) schemes require the adoption of new protocols and procedures for Maximum Power Extrapolation (MPE) techniques. Considering that SS/PBCH (Synchronization Signal/Physical Broadcast Channel) block is the only 'lways-on' signal in 5G NR, several proposals use it as a reference in Extrapolation Techniques (ETs). Therefore, it is important to analyze its variability in the case of measurements on the field for analysing its stability and quantifying if it could affect the accuracy of the achieved results (thus making unreliable the comparison against applicable limits). In this framework, this paper reports the experimental analyses based on the use of a vectorial network scanner for collecting the Synchronization Signal Reference Signal Received Power (SS- RSRP) of the Sec-ondary Synchronization Signal (SSS) in the Broadcast Channel (PBCH) of the SS/PBCH block over several days for several mobile operators. The measurement campaign showed different behaviours among the operators and also proved how, in many cases, the variability ranges of SS- RSRP significantly exceed the typical measurement uncertainty.